Dewaxing hydrocarbon oil



Patented July 14, 1936 UNITED STATES ATENT OFFIE' DEWAXING HYDROC'ARBON OIL Howard H. Gross and Walter V. Overbaugh,

Beacon, N. Y., assignors to The Texas Company, New York, N. Y., a corporation of Dela- This invention relates to dewaxing hydrocarbon oil, and more particularly to the removal of wax from mineral lubricating oil stock for the production of low pour test lubricating oils.

5 The invention contemplates a solvent dewaxing process wherein a solvent of the character of methyl isobutyl ketone is employed as the dewaxing solvent. The solvent compound of our invention is one having the chemical formula: (CH3)2 CHCH2COCH3, and may comprise a com mercial grade of product having a specific gravity of about 0.799 to 0.804 at 20/20 C. with a boiling point of from about 113 to 119 C.

More specifically, the invention comprises mixing a wax-bearing mineral oil fraction with a solvent comprising methyl isobutyl ketone in proportions such that at temperatures of F. and below the solvent has substantially complete solvent action on the liquid constituents of the oil and substantially no solvent action upon the solid waxy constituents of the oil. This mixture is then chilled to temperatures ranging from 0 to 20 F. or lower, depending upon the desired pour test of the dewaxed oil, to precipitate the wax constituents. The precipitated wax constituents are then separated from the cold mixture by mechanical means, such as filtration, centrifuging or settling.

It has been discovered that methyl isobutyl ketone possesses properties which render it suitable as a dewaxing solvent. This solvent has anti-solvent properties for paraffin wax and, in addition, possesses relatively high solvent power for mineral oil so that it may be employed alone as a satisfactory dewaxing solvent liquid. Its selective solvent action as between solid and liquid hydrocarbon constituents of wax-bearing mineral oil at temperatures of 0 F. and below is such that when dewaxing with this solvent liquid, 40 there is no substantial temperature diiferential between the dewaxing temperature and the pour temperature of the resulting dewaxed oil.

In order to more clearly describe the invention, reference will now be made to the following example in which a wax-bearing distillate, derived from Mid-Continent crude, having a pour test of around 95 F. and a Saybolt universal viscosity at 210 F. of about '72 to 74 seconds was dewaxed with methyl isobutyl ketone.

One volume of the foregoing wax-bearing distillate was mixed with about four volumes of commercial methyl isobutyl ketone. The resulting mixture was chilled to a temperature of l2 F. to precipitate the wax constituents and, while maintained at this temperature, the cold mixture was filtered to separate the precipitated wax constituents.

The solvent was then removed from the dewaxed filtrate and the dewaxed oil thus recovered amounted to about 72% by volume of the 5 original wax-bearing distillate and had a pour test of F.

While in the foregoing example, dewaxing with a ketone solvent alone has been described, it is contemplated that, in the case of certain oils, 10 it may be advantageous to employ the solvent in combination with suitable modifying solvent liquids as, for example, solvents of the character of benzol or its homologs, or light petroleum fractions such as propane, butane and natural gasoline hydrocarbons.

Thus, in the case of heavy viscous oils, it may be desirable to add benzol or a light petroleum fraction to the mixture to prevent objectionable oil separation from the mixture at the dewaxing temperature, and also to serve as a diluent, and thereby facilitate separation of the wax from the mixture.

The solvent of our invention may be adapted to the separation of wax from crude petroleum, or from either residual or distillate fractions thereof. It may also be adapted to the treatment of wax concentrates, such as petrolatum, for the purpose of effecting separation between the wax and oil constituents.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In the dewaxing of wax-bearing mineral oil, the method which comprises mixing the oil with a solvent comprising methyl isobutyl ketone in proportions with the oil such that at temperatures of the order of 0 F., the solvent has substantially complete solvent action for the liquid hydrocarbon constituents of the oil and substantially no solvent action for the wax constituents of the oil, chilling the mixture to precipitate the wax constituents, and separating the precipitated wax constituents from the cold mixture.

2. In the dewaxing of wax-bearing mineral oil, the method which comprises mixing the oil with methyl isobutyl ketone, chilling the mixture to temperatures of 0 F. and below to precipitate the wax constituents, and separating the thus pre- 55 the method which comprises mixing the oil with commercial methyl isobutyl ketone in proportions up to about four parts of ketone to one part of oil, chilling the mixture to a. tempera.- ture of the order of -10 F. to precipitate the wax constituents, and removing the precipitated wax constituents from the cold mixture.

HOWARD H. GROSS. WALTER V. OVERBAUGH. 

